Need a new direction on speedo, I have an 86 formula was a 2.8 5 speed, installed a 350 carb, put a cluster from a v8, and t5 nwc from a v8 (the speedo was correct in donor car before removed)installed a 3.23 posi , (not sure what it was out of) problem I'm have is speedo works but is off(too slow) I kept the orginal ecm and yellow buffer box. I ran a new 2 wire harness from the vss, I have 1 connected to chassis ground and the other to the green wire, now I see from this pic it is connected direct to the speedo in cluster, This seems to be the only way I can get any action out of the speedo head. I tried connecting to yellow and purple but no action seen on speedo, Is this the only 2 wires it should be connected to? if so I should assume the buffer box is NFG right?